JP2021044860A - All solid lithium ion secondary battery system, and charging device for all solid lithium ion secondary battery - Google Patents

Abstract

To provide means capable of detecting an increase of internal resistance of an all solid battery when charging the battery, and continuing the charge after the increased internal resistance is reduced.SOLUTION: When an all solid lithium ion secondary battery is to be charged by a charger, in the case where an internal resistance value of the battery or an increase rate with respect to an initial internal resistance value is equal to or higher than a predetermined threshold, the battery is charged with a heating current which is greater than a rating charging current.SELECTED DRAWING: Figure 3

Description

The present invention relates to an all-solid-state lithium-ion secondary battery system and a charging device for an all-solid-state lithium-ion secondary battery.

In recent years, there is an urgent need to reduce the amount of carbon dioxide in order to cope with global warming. In the automobile industry, expectations are high for the reduction of carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and non-water batteries such as secondary batteries for driving motors, which hold the key to their practical application. The development of secondary electrolyte batteries is being actively carried out.

The secondary battery for driving a motor is required to have extremely high output characteristics and high energy as compared with a consumer lithium ion secondary battery used in mobile phones, notebook computers, and the like. Therefore, the lithium-ion secondary battery, which has the highest theoretical energy among all realistic batteries, is attracting attention and is currently being rapidly developed.

Here, the lithium ion secondary battery currently widely used uses a flammable organic electrolyte as an electrolyte. In such a liquid-based lithium-ion secondary battery, safety measures against liquid leakage, short circuit, overcharge, etc. are required more strictly than other batteries.

Therefore, in recent years, research and development on an all-solid-state lithium-ion secondary battery (hereinafter, also referred to as "all-solid-state battery") using an oxide-based or sulfide-based solid electrolyte as an electrolyte has been actively carried out. The solid electrolyte is a material composed mainly of an ionic conductor capable of conducting ions in a solid. Therefore, in the all-solid-state lithium ion secondary battery, various problems caused by the flammable organic electrolytic solution do not occur in principle unlike the conventional liquid-based lithium ion secondary battery. Further, in general, when a high potential / large capacity positive electrode material and a large capacity negative electrode material are used, the output density and energy density of the battery can be significantly improved. An all-solid-state battery using a sulfide-based material as the positive electrode active material and metallic lithium or a lithium-containing alloy as the negative electrode active material is a promising candidate.

By the way, in a lithium ion secondary battery, the internal resistance increases as the charge / discharge cycle is repeated. When the internal resistance of the battery rises, there is a problem that it becomes difficult to take out a large current, a problem that it takes a long time to charge, and a problem that the battery tends to generate heat and as a result, the deterioration of the battery tends to progress. .. Therefore, suppressing an increase in the internal resistance of the lithium ion secondary battery is important from the viewpoint of extending the life of the battery.

As a technique for suppressing an increase in internal resistance with the progress of a charge / discharge cycle in an all-solid-state battery, Patent Document 1 describes a layered region that gradually expands as the charge amount increases and a layered region that gradually expands as the charge amount increases. A method for charging an all-solid-state battery is disclosed, which uses a negative electrode active material having a Li ion insertion site composed of a rapidly expanding pore region and uses only the layered region in normal charging. According to Patent Document 1, by adopting the above-described configuration, deterioration of contact between the negative electrode active material and the solid electrolyte during charging is suppressed, and as a result, an increase in internal resistance with the progress of the charge / discharge cycle is suppressed. It is said that it can be done.

Japanese Unexamined Patent Publication No. 2016-154104

The present inventors have diligently searched for the cause of the increase in internal resistance in an all-solid-state battery. As a result, in addition to the deterioration of the contact state between the active material and the solid electrolyte studied in Patent Document 1, minute cracks are generated in the solid electrolyte layer and the interface between the electrode active material layer and the solid electrolyte layer is formed. It was found that the increase in ohmic resistance due to peeling was the dominant cause.

There is a problem that the internal resistance increased due to these dominant causes cannot be reduced (recovered) by the technique proposed in Patent Document 1. Further, the technique disclosed in Patent Document 1 does not include a detection circuit for determining whether the Li ion insertion site used for charging belongs to the layered region or the pore region. Therefore, there is also a problem that it is difficult to determine whether or not it is possible to suppress an increase in internal resistance depending on the charging method disclosed in Patent Document 1.

An object of the present invention is to provide a means for detecting an increase in the internal resistance of an all-solid-state battery when charging the battery, reducing the increased internal resistance, and then continuing charging. is there.

The present inventors have made diligent studies to solve the above problems. As a result, when charging the all-solid-state lithium-ion secondary battery, the internal resistance value of the battery is measured, and the measured internal resistance value or the rate of increase with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. At that time, it was found that the above problem can be solved by controlling the battery to be charged with a heating current larger than the rated charging current, and the present invention has been completed.

In the all-solid-state lithium ion secondary battery system according to one embodiment of the present invention, first, a positive electrode including a positive electrode active material layer containing a positive electrode active material, a negative electrode including a negative electrode active material layer containing a negative electrode active material, and the above. An all-solid lithium ion secondary battery including a power generation element having a positive electrode active material layer and a solid electrolyte layer interposed between the negative electrode active material layer is provided. Further, the system includes a charger for charging the all-solid-state lithium-ion secondary battery, an internal resistance measuring unit for measuring the internal resistance of the all-solid-state lithium-ion secondary battery, and a control unit for controlling the charger. To be equipped. Then, when the charger charges the all-solid-state lithium-ion secondary battery, the control unit determines in advance the internal resistance value measured by the internal resistance measuring unit or the rate of increase with respect to the initial internal resistance value. When the value is equal to or higher than the threshold value, the charger is controlled so as to charge the all-solid-state lithium-ion battery with a heating current larger than the rated charging current.

The charging device for the all-solid-state lithium-ion secondary battery according to another embodiment of the present invention includes a charger for charging the all-solid-state lithium-ion secondary battery and an internal measuring device for measuring the internal resistance of the all-solid-state lithium-ion secondary battery. It includes a resistance measuring unit and a control unit that controls the charger. Then, when the charger charges the all-solid-state lithium-ion secondary battery, the control unit determines in advance the internal resistance value measured by the internal resistance measuring unit or the rate of increase with respect to the initial internal resistance value. When the value is equal to or higher than the threshold value, the charger is controlled so as to charge the all-solid-state lithium-ion battery with a heating current larger than the rated charging current.

According to the present invention, when charging an all-solid-state battery, it is possible to detect an increase in the internal resistance of the battery, reduce the increased internal resistance, and then continue charging. As a result, the occurrence of various problems caused by an increase in internal resistance can be prevented, which can contribute to shortening the charging time and extending the life of the battery.

It is a block diagram for demonstrating the structure of the all-solid-state lithium ion secondary battery system which concerns on one Embodiment of this invention. It is a system schematic diagram of the electric system of the electric vehicle equipped with the all-solid-state lithium ion secondary battery system which concerns on one Embodiment of this invention. It is a flowchart which shows the procedure of the quick charge process in a secondary battery system 1. _{A graph for explaining an example of a method of calculating the battery temperature T from the measured temperature T m of the} secondary battery by the temperature sensor (vertical axis is temperature; horizontal axis is the position inside the battery that is the battery temperature T to be calculated (temperature estimation). Distance from position). It is a block diagram of the power supply circuit in the idling stop vehicle which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the whole structure of the all-solid-state lithium ion secondary battery (stacked type secondary battery) of the laminated type (internal parallel connection type) which is one Embodiment of this invention. It is sectional drawing which represented typically the bipolar type (bipolar type) all-solid-state lithium ion secondary battery (bipolar type secondary battery) which concerns on one Embodiment of this invention. It is a perspective view which showed the appearance of the flat lithium ion secondary battery which is a typical embodiment of a laminated type secondary battery.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following embodiments. The dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

[Secondary battery system]
FIG. 1 is a block diagram for explaining the configuration of an all-solid-state lithium-ion secondary battery system according to an embodiment of the present invention. FIG. 2 is a system schematic diagram of an electric system of an electric vehicle equipped with an all-solid-state lithium-ion secondary battery system according to an embodiment of the present invention.

With reference to FIG. 1, this all-solid-state lithium-ion secondary battery system (hereinafter, also referred to as “secondary battery system 1”) is an all-solid-state lithium-ion secondary battery (hereinafter, also referred to as “secondary battery 2”). To be equipped. Then, charging power is supplied to the voltage sensor 3 that measures the cell voltage (voltage between terminals) of the secondary battery 2, the temperature sensor 4 that measures the outer surface temperature (environmental temperature) of the secondary battery 2, and the secondary battery 2. It includes a voltage / current adjusting unit 5, a current sensor 6 that measures the charge / discharge current of the secondary battery 2, and a control unit 7 that controls the charge / discharge of the secondary battery 2. Further, the voltage / current adjusting unit 5 is connected to the external power source 8 and receives power during charging, while discharging to the external power source 8 side via the voltage / current adjusting unit 5 during discharging (details will be described later).

With reference to FIG. 2, the secondary battery 2 is usually stored in the battery pack 100 in the form of a secondary battery module (assembled battery) 110. The battery pack 100 is equipped with a battery management (battery control) system (BMS) 120. The BMS 120 includes a voltage sensor 3, a temperature sensor 4, a current sensor 6, and the like, and transmits information on the battery pack 100 and the secondary battery 2 (secondary battery module 110) to a higher-level control unit 7, and instructs the BMS 120. Is received to control the battery pack 100 and the secondary battery 2 (secondary battery module 110). That is, the BMS 120 also functions as a control unit in the present invention. The battery pack 100 further includes a junction box 130 for controlling disconnection of the secondary battery module 110 from the high-power circuit, and the junction box 130 is controlled by the control unit 7.

The electric vehicle is also equipped with a DC / DC junction box 200. The DC / DC junction box 200 is equipped with a DC / DC converter 210 for converting a high voltage from the secondary battery 2 (secondary battery module 110) into a low voltage. Further, the DC / DC junction box 200 controls the connection disconnection of the secondary battery 2 (secondary battery module 110) to the normal charging system and the normal charging relay 220 for controlling the connection disconnection to the quick charging system. It is further equipped with a quick charge relay 230 for the purpose. The normal charging relay 220 is connected to the normal charging port 222 via the vehicle-mounted charger 221 and the quick charging relay 230 is directly connected to the quick charging port 232.

The details of each part shown in FIG. 1 will be described below.

The secondary battery 2 is a normal all-solid lithium ion secondary battery, and has a positive electrode including a positive electrode active material layer containing a positive electrode active material, a negative electrode including a negative electrode active material layer containing a negative electrode active material, and the positive electrode. A power generation element having a solid electrolyte layer interposed between the active material layer and the negative electrode active material layer is provided. The details of the all-solid-state lithium-ion secondary battery will be described later.

The voltage sensor 3 may be, for example, a voltmeter, and measures the cell voltage (voltage between terminals) between the positive electrode and the negative electrode of the secondary battery 2. The cell voltage (voltage between terminals) measured when the secondary battery 2 is not energized is the open circuit voltage (OCV) of the secondary battery 2. On the other hand, the cell voltage (voltage between terminals) measured during charging / discharging of the secondary battery 2 is this open circuit by the amount of the voltage drop (ΔV = ΔI × R) caused by the internal resistance (R) of the secondary battery 2. It is a value changed from the voltage (OCV). That is, the voltage sensor 3 can function as an SOC detection unit or an OCV detection unit. The mounting position of the voltage sensor 3 is not particularly limited as long as it is a position where the cell voltage between the positive electrode and the negative electrode can be measured in the circuit connected to the secondary battery 2.

The temperature sensor 4 measures the outer surface temperature (environmental temperature) of the secondary battery 2. The temperature sensor 4 is attached to, for example, the surface of the case (exterior body, housing) of the secondary battery 2. In the present embodiment, the temperature of the secondary battery 2 is acquired by the control unit 7 described later estimating the temperature inside the secondary battery 2 from the outer surface temperature of the secondary battery 2 measured by the temperature sensor 4. To do. That is, the temperature sensor 4 and the control unit 7 function as a temperature detection unit that detects the temperature of the secondary battery 2.

When charging the secondary battery 2, the voltage / current adjusting unit 5 adjusts the voltage and current of the electric power from the external power source 8 based on the command from the control unit 7, and supplies the electric power to the secondary battery 2. Further, when the secondary battery 2 is discharged, the voltage / current adjusting unit 5 discharges the electricity discharged from the secondary battery 2 to the external power supply 8 side. In this way, the voltage / current adjusting unit 5, the external power supply 8, and the control unit 7 described later function as a charger for charging the secondary battery 2.

Here, the external power source 8 is a power source for an electric vehicle used for charging an electric vehicle or the like, a so-called power grid or the like, and direct current is output. Such a power source for an electric vehicle is provided by converting commercial electric power (alternating current) into direct current having a voltage and a current required for charging the secondary battery 2. Further, the external power source 8 is provided with a power regeneration function, and when there is a discharge from the secondary battery 2, the direct current can be converted into an alternating current and regenerated to a commercial power source. As the device constituting such an external power source 8, a well-known power source having a power regeneration function may be used, and therefore detailed description thereof will be omitted here (as a power source having a power regeneration function, the power source has a power regeneration function. For example, some are disclosed in JP-A-7-2223669, JP-A-10-080067, and the like).

When the external power supply 8 is not connected to an external power supply device such as a commercial power supply, for example, when charging the secondary battery 2 using another secondary battery installed externally as a power source, the power discharged from the secondary battery 2 Is preferably stored in another secondary battery. This can reduce the waste of energy.

The current sensor 6 is, for example, an ammeter. The current sensor 6 measures the current value of the electric power supplied from the voltage / current adjusting unit 5 to the secondary battery 2 when the secondary battery 2 is charged, and is supplied from the secondary battery 2 to the voltage / current adjusting unit 5 when discharging. Measure the current value of power. The mounting position of the current sensor 6 is not particularly limited, as long as it is located in a circuit that supplies power from the voltage / current adjusting unit 5 to the secondary battery 2 and can measure the current value during charging / discharging. Good.

The control unit 7 is a so-called computer including, for example, a CPU 71 and a storage unit 72. The control unit 7 controls the charger when charging the secondary battery 2 according to a procedure described later, and adjusts the conditions of the charging process and the like. As such a control unit 7, in an electric vehicle, for example, an ECU (Electronic Control Unit) or the like may be used. When the secondary battery 2 is mounted on a vehicle, the secondary battery 2 and the control unit 7 may be mounted on the vehicle, and the charger may be installed outside the vehicle. Further, the charger may be installed outside the vehicle, and the control unit 7 may also be mounted on the charger.

Here, the storage unit 72 is equipped with a non-volatile memory in addition to the RAM used by the CPU 71 as a working area. The non-volatile memory stores a program for controlling the charger (adjusting the conditions of charging processing) in the present embodiment.

The storage unit 72, the control of the charger in the present embodiment is referred to when performing the (regulation of conditions of the charging process), the initial internal resistance value R ₁ of the rechargeable battery _2, as well as, the secondary battery 2 _{The threshold value (R't} ) for the rate of increase R'with respect to the initial internal resistance value R _{1 of the internal resistance value R and the threshold value (T t} ) for the battery temperature T of the secondary battery 2 are stored. Further, the storage unit 72 stores a map (hereinafter, also referred to as “first map”) showing the relationship between the battery voltage V of the secondary battery 2 and the charge state (SOC; State of Charge) of the secondary battery. There is.

[Charging process]
The procedure of the charging process in the secondary battery system 1 configured as described above will be described.

This charging process is performed in a state in which the secondary battery system 1 is connected to the external power source 8 and charging power can be supplied to the secondary battery 2. Further, the control of the charging process in the present embodiment is a constant current (CC) charging method in which the voltage of the secondary battery 2 reaches a predetermined voltage. However, the form of the charging process is not limited to this, and charging is performed by the constant current (CC) charging method, and after the voltage of the secondary battery 2 reaches a predetermined voltage, the constant voltage (CV) charging method is used. A current / constant voltage (CC-CV) charging method may be used.

In the control in the present embodiment, when the charger charges the secondary battery 2 (specifically, before charging the secondary battery 2 with the rated charging current, or before charging the secondary battery 2 with the rated charging current, or when the secondary battery 2 is charged with the rated charging current. (While charging with the battery), it is determined whether or not the rate of increase of the internal resistance value measured by the internal resistance measuring unit with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. Then, when the rate of increase of the internal resistance value with respect to the initial internal resistance value is equal to or greater than the threshold value, the charger is controlled so as to charge the secondary battery 2 with a heating current larger than the rated charging current. .. Unless otherwise specified, this charging process (control of the charger) is performed by the control unit 7. Hereinafter, the procedure of this control in the case of performing quick charging will be described with reference to FIG. FIG. 3 is a flowchart showing a procedure of quick charging processing in the secondary battery system 1.

First, the control unit 7 turns on the quick charge relay 230 (step S101). Subsequently, the control unit introduces electric power from the external power source 8 to the voltage / current adjusting unit 5 and applies a charging current (pulse current) of about several seconds to the secondary battery 2 (step S102). The charging current (pulse current) applied at this time is applied for the purpose of calculating the internal resistance value R of the secondary battery 2. Therefore, the pulse current may be used because it does not need to be applied for a long time. Further, the value of the charging current (pulse current) is not particularly limited as long as the internal resistance value R can be calculated.

Next, the control unit 7 acquires the charging current I from the current sensor 6 and the battery voltage V from the voltage sensor 3. Then, the control unit 7 calculates the internal resistance value R (= V / I) of the secondary battery 2 from Ohm's law based on these acquired values, and also calculates the internal resistance value R of the secondary battery 2. The rate of increase R'with respect to the initial internal resistance value R _{1 is calculated (step S103).} Here, the rate of increase R'is
R'= (R-R ₁ ) / R ₁ x 100
It is expressed as.

Further, in the present embodiment, the control unit 7 is a "map showing the relationship between the battery voltage V of the secondary battery 2 and the charge state (SOC) of the secondary battery" stored in the storage unit 82 (first map). Based on the battery voltage V acquired from the voltage sensor 3, the SOC of the secondary battery 2 is calculated and acquired (step S103).

Further, in the present embodiment, the control unit 7 calculates the internal temperature (battery temperature T) of the secondary battery 2 from _{the measured temperature T m acquired from the temperature sensor 4 and acquires this (step S103).} At this time, the control unit 7 of the secondary battery detected by the temperature sensor 4 based on the thermal resistance value (thermal conductivity) between the temperature detection position by the temperature sensor 4 and the power generation element of the secondary battery 2. Correct the measurement temperature T _{m. Here, FIG. 4 is a graph for explaining an example of a method of calculating the battery temperature T from the measured temperature T m} of the secondary battery 2 by the temperature sensor 4 (vertical axis is temperature; horizontal axis is the battery temperature T to be calculated). (Distance from the position inside the battery (estimated temperature position)). As shown in FIG. 4, the distance from the temperature estimated position until the battery surface and [Delta] x _1, the measurement position by the temperature sensor 4 (e.g., the surface of the battery case) a distance to a [Delta] x ₂ from the battery surface, on both sides of the battery surface _Let T s1 and T _s2 (T _s1 > T _s2 ), respectively. _{Then, the heat transfer coefficients h 1} and h _{2 on} the surface of the battery and the surface of the battery case, which are all known parameters, the thermal conductivity λ _{c in} the battery, the thermal conductivity λ _M from the battery to the measurement position, and the measurement. Using the temperature T _m and the outside air temperature T _∞ , the heat flux J in this system is
J = λ _c ( _{TT s1} ) / Δx ₁
J = h ₁ (Ts _{1- Ts 2} )
J = λ _M (Ts _2- T _∞ ) / Δx ₂
J = h ₂ ( _Tm −T _∞ )
It is expressed as. By solving these for T, the battery temperature T can be calculated. By performing the following control using the battery temperature T corrected in this way, more precise control becomes possible.

In the present embodiment, the control unit 7, followed by increasing rate R of the internal resistance value calculated by the comparison with _t 'and threshold R stored in the storage unit 72 is determined in advance', R 'is R' it determines whether or not _t or more (step S104). Here, if it is determined that R 'is R' less than _{t (R '<R' t} ) (S104: NO), and terminates the increase rate R 'control based on the internal resistance value in the next step move on. This is because the rate of increase R'of the internal resistance value of the secondary battery 2 is sufficiently low (and the absolute value of the internal resistance value R) is sufficiently low, so that various problems due to the high internal resistance value may occur. It means that it is regarded as not. In this case, the control unit 7 introduces electric power from the external power supply 8 to the voltage / current adjusting unit 5, applies the rated charging current to the secondary battery 2, and starts the main charging (step S105).

When the main charging is started in step S105, the control unit 7 acquires the battery voltage V from the voltage sensor 3 and refers to the first map stored in the storage unit 82 to obtain the battery voltage from the voltage sensor 3. Based on V, the SOC of the secondary battery 2 is calculated and acquired (step S106). After that, the control unit 7 determines whether or not the SOC value of the secondary battery 2 calculated in step S106 is larger than the preset target SOC as a value sufficient to end the charging process (SOC> target SOC). (Step S107). Here, if it is determined that the SOC value of the secondary battery 2 is larger than the target SOC (SOC> target SOC) (S107: YES), the control unit 7 controls the voltage / current adjusting unit 5 to charge the battery. The process is completed and the quick charge relay is turned off (step S108).

On the other hand, if it is not determined in step S107 that the value of the SOC of the secondary battery 2 is larger than the target SOC (SOC> target SOC) (S107: NO), the control unit 7 repeats the control from step S103.

On the other hand, if it is determined that the rate of increase in the internal resistance value R R 'threshold R' is _t or more in step _{S104 (R '≧ R' t} ) (S104: YES), the control unit 7, the external power source Electric power is introduced from 8 to the voltage / current adjusting unit 5, and a current (heating current) larger than the rated charging current is applied to the secondary battery 2 (step S110). Generally, when a current is applied to the secondary battery 2, ^{Joule heat calculated by Q = RI 2} × t (R is the resistance value, I is the current value, and t is the time) is generated. Greater than the rated charging current. Therefore, when the heating current is applied, a larger amount of Joule heat is generated inside the battery than when charging with the rated charging current. As a result, the internal temperature of the battery (battery temperature T) rises, and when the internal temperature of the battery rises to near the melting point of a certain material constituting the power generation element, the material melts. In the present embodiment, this is utilized to reduce (recover) the internal resistance of the secondary battery 2. Specifically, for example, comparing the melting points of the solid electrolyte, which is the main constituent material of the secondary battery 2, with the melting points of the active materials of the positive electrode and the negative electrode, the solid electrolyte composed of oxides and sulfides is the one. Usually has a higher melting point. The melting point of sulfur (S) preferably used as the positive electrode active material is 115.2 ° C., and the melting point of the metallic lithium simple substance (Li) preferably used as the negative electrode active material is 180.5 ° C. is there. Therefore, when the internal temperature of the secondary battery 2 is raised to near the melting point (115.2 ° C.) of the lowest sulfur (S) among these, sulfur (S), which is the positive electrode active material, melts. By melting the positive electrode active material (sulfur (S)) in this way, fluidity is generated at the interface between the positive electrode active material layer and the solid electrolyte layer, and the contact state between these layers is improved. As a result, the ohmic resistance (interfacial resistance) between these layers is reduced, and the internal resistance of the secondary battery 2 is reduced (recovered). By applying the rated charging current to the secondary battery 2 whose internal resistance has been reduced (recovered) in this way to perform main charging, there is an advantage that the charging time can be shortened.

As described above, the application of the heating current raises the internal temperature (battery temperature T) of the secondary battery 2 to near the melting point of the constituent material of the power generation element, but raises it to a value exceeding this melting point. Then, the material melts and the shape of the power generation element cannot be maintained. Therefore, when the control unit starts applying the heating current in step S110, the control unit _{acquires the measured temperature T m} from the temperature sensor 4, calculates the battery temperature T by the same method as described above, and acquires the measured temperature T (step). S111). Then, the control unit 7 compares the battery temperature T thus acquired with the threshold temperature T _t stored in the storage unit 72 in advance, and determines whether or not T is T _{t or more.} (Step S112) At this time, _{there is no particular limitation on the specific value of the threshold temperature T t} , which is sufficiently high to reduce the internal resistance value of the secondary battery 2 and which is among the melting points of the constituent materials of the power generation element. The value may be sufficiently lower than the lowest value (115.2 ° C., which is the melting point of sulfur (S) in the above case).

Here, if it is determined that the battery temperature T is _{equal to} or higher than the _{threshold temperature T t (T ≧ T t} ) (S112: YES), it is considered that the internal resistance value of the secondary battery 2 is sufficiently reduced. Can be done. Therefore, in this case, the control unit 7 controls the voltage / current adjusting unit 5 to stop the application of the heating current to stop the charging with the heating current (step S113), and control from step S102. repeat. By setting the threshold temperature T _t in this way and stopping charging with the heating current when the battery temperature T of the secondary battery 2 _{becomes equal to} or higher than the threshold temperature T t, the positive electrode after the application of the heating current is stopped. The maximum temperature of the active material and the negative electrode active material can be prevented from being higher than or lower than the respective melting points (being lower than the respective melting points). As a result, melting of the active material component and accompanying destruction of the shape of the power generation element are prevented. In order to enable this control, the control unit 7 controls the magnitude of the heating current and / or the application time of the heating current in the present embodiment.

On the other hand, if it is determined in step S112 that the battery temperature T is _{less than the threshold temperature T t} (T <T _t ) (S112: NO), the control unit 7 repeats the control from step S111.

Although the control according to the present invention has been described in detail above, the embodiment described with reference to the drawings is merely an example, and is appropriately modified within the scope of the technical idea of the invention described in the claims. The present invention may be carried out. For example, in the embodiment described above, set the _t 'threshold R of' battery increase rate R of the internal resistance value was determine the necessity of applying the heating current so as reference. _{However, the threshold value R t} of the absolute value of the internal resistance value is set without using the rate of increase as an index, and the threshold value R is compared with the measured value R of the internal resistance value of the battery based on this, and the heating current is applied. You may decide whether it is necessary or not. Further, it has been described above that the dominant cause of the increase in the internal resistance value in the all-solid-state battery is the increase in the ohmic resistance (interface resistance) due to the separation between the electrode active material layer and the solid electrolyte layer. Here, in the measurement of the internal resistance value based on Ohm's law as described above, the ohmic resistance (interfacial resistance) cannot be separated from the measured internal resistance value and used for control. On the other hand, the internal resistance value is measured by using the electrochemical impedance measurement method (EIS), and the electrolyte resistance component calculated from the Cole-Cole plot is regarded as the internal resistance value, and the control of the present invention is carried out. It is possible to control using a resistance value close to the ohmic resistance (interfacial resistance) between the electrode active material layer and the solid electrolyte layer, which is a typical factor, as an index. However, the measurement based on Ohm's law described above has an advantage that on-board control is possible in an in-vehicle secondary battery system or the like.

Further, in the above-described embodiment, the secondary battery 2 is mounted on the vehicle, and the charger is connected to the secondary battery 2 by using the electric power supplied from the power source (external power source 8) installed outside the vehicle. Apply a heating current. According to such an embodiment, the soundness (SOH; State of Health) of the secondary battery 2 can be confirmed for each charge, and the rate of increase in the internal resistance value can be constantly monitored. There is an advantage that resistance can be reduced (recovered).

However, even when the secondary battery 2 is mounted on the vehicle, the charger uses the power supplied from another power source mounted on the vehicle instead of the external power supply 8 to use the secondary battery 2. A heating current may be applied to the battery. For example, in an electric vehicle in which the secondary battery 2 as shown in FIG. 2 is used as a high-power battery, a lead-acid battery mounted as a low-power battery (so-called 12V battery), a conventional non-aqueous electrolyte lithium-ion secondary battery, or the like is used. It can be used as "another power source mounted on a vehicle". According to such an embodiment, even in a situation where the external power source 8 cannot be accessed, for example, while driving, the soundness (SOH) of the secondary battery 2 is determined and the presence or absence of an increase in internal resistance is detected. It is possible to reduce (recover) the internal resistance of the secondary battery 2 onboard by applying a heating current from the light electric battery as needed.

Further, an example of another embodiment in which a heating current is applied to the secondary battery 2 by using the electric power supplied from another power source mounted on the vehicle will be described with reference to FIG.

FIG. 5 is a block diagram of a power supply circuit in an idling stop vehicle according to an embodiment of the present invention. The power supply circuit 300 is a circuit that supplies electric power to the starter motor (SM) 240 and other electrical loads 250, and includes a main battery 310, a sub-battery 320, and a relay 330. It is assumed that the power supply circuit 300 also supplies electric power to the controller (not shown).

As the main battery 310, for example, a lead storage battery is used. Lead dioxide is used for the positive electrode of the lead-acid battery, spongy lead is used for the negative electrode, and dilute sulfuric acid is used for the electrolytic solution. The main battery 310 is charged by the regenerative power generated by the alternator (ALT) 260, and the open circuit voltage in the fully charged state is, for example, 12.7 V.

The sub-battery 320 is provided to prevent the power supply voltage of the vehicle from being momentarily lowered due to the large current flowing through the starter motor (SM) 240 when the engine (not shown) is restarted from the idling stop. In the present embodiment, the all-solid-state lithium-ion secondary battery 2 is used as the sub-battery 320. The sub-battery 320 is charged by the regenerative power generated by the alternator (ALT) 260, and the open circuit voltage in the fully charged state is, for example, 13.1 V.

The relay 330 is a switch for switching whether the sub-battery 320 is connected to the power supply circuit 300 or disconnected from the power supply circuit 300, and is controlled by a controller (not shown). The relay 330 is a normally open a-contact, and disconnects the sub-battery 320 from the power supply circuit 300 when the contact is open, and connects the sub-battery 320 to the power supply circuit 300 when the contact is closed. Specifically, while the engine is in operation, the sub-battery 320 is connected to the power supply circuit 300, and the electric power supplied from the alternator (ALT) 260 is charged to the sub-battery 320. Further, when the engine is restarted from the idling stop, the sub-battery 320 is connected to the power supply circuit 300, and the electric power from the sub-battery 320 is supplied to the starter motor (SM) 240. In addition, the sub-battery 320 is connected to or cut off from the power supply circuit 300 as needed.

In such an embodiment, for example, a lead-acid battery mounted as the main battery 310 can be used as "another power source mounted on the vehicle". An alternator (ALT) 260 that generates regenerative power can also be used as "another power source mounted on the vehicle". According to these embodiments, even in a situation where the external power source 8 cannot be accessed, for example, while driving, it is necessary to determine the soundness (SOH) of the secondary battery 2 and detect the presence or absence of an increase in the internal resistance. It is possible to reduce (recover) the internal resistance of the secondary battery 2 as the sub-battery 320 onboard by applying a heating current from the main battery 310 (lead-acid battery) or the alternator (ALT) 260 according to the above. ..

According to another embodiment of the present invention, a charging device (charging device for an all-solid-state lithium ion secondary battery) for charging the above-mentioned secondary battery 2 is provided. The charging device for charging the all-solid-state lithium-ion secondary battery includes a charger for charging the all-solid-state lithium-ion secondary battery, an internal resistance measuring unit for measuring the internal resistance of the all-solid-state lithium-ion secondary battery, and an internal resistance measuring unit. When the charger charges the all-solid-state lithium-ion secondary battery, when the internal resistance value measured by the internal resistance measuring unit or the rate of increase with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. It is provided with a control unit that controls the charger so as to charge the all-solid-state lithium-ion battery with a heating current larger than the rated charging current.

Further, according to still another embodiment of the present invention, a method for charging the secondary battery for charging the secondary battery 2 described above is also provided. The method of charging the all-solid-state lithium-ion secondary battery is that when the charger charges the all-solid-state lithium-ion secondary battery, the increase rate with respect to the internal resistance value of the all-solid-state lithium-ion secondary battery or its initial internal resistance value. Includes charging the all-solid-state lithium-ion battery with a heating current greater than the rated charging current when is greater than or equal to a predetermined threshold.

Hereinafter, the all-solid-state lithium-ion secondary battery constituting the all-solid-state lithium-ion secondary battery system according to the present embodiment will be described.

FIG. 6 schematically shows the overall structure of a laminated (internal parallel connection type) all-solid-state lithium-ion secondary battery (hereinafter, also simply referred to as “laminated secondary battery”) according to an embodiment of the present invention. It is a cross-sectional view. The laminated secondary battery 10a shown in FIG. 6 has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminated film 29 which is a battery exterior.

As shown in FIG. 6, the power generation element 21 of the laminated secondary battery 10a of the present embodiment includes a positive electrode in which positive electrode active material layers 13 are arranged on both sides of the positive electrode current collector 11', a solid electrolyte layer 17, and a negative electrode. It has a structure in which a negative electrode in which a negative electrode active material layer 15 is arranged is laminated on both sides of a current collector 11 ″. Specifically, the positive electrode, the solid electrolyte layer, and the negative electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other via the solid electrolyte layer 17. ing. As a result, the adjacent positive electrode, solid electrolyte layer, and negative electrode form one cell cell layer 19. Therefore, it can be said that the laminated secondary battery 10a shown in FIG. 6 has a configuration in which a plurality of single battery layers 19 are laminated and electrically connected in parallel. The positive electrode current collectors in the outermost layers located in both outermost layers of the power generation element 21 have the positive electrode active material layer 13 arranged on only one side, but active material layers may be provided on both sides. .. That is, instead of using a current collector dedicated to the outermost layer in which the active material layer is provided on only one side, a current collector having active material layers on both sides may be used as it is as the current collector in the outermost layer. Further, by reversing the arrangement of the positive electrode and the negative electrode as in FIG. 6, the negative electrode current collector of the outermost layer is located on both outermost layers of the power generation element 21, and one side of the negative electrode current collector of the outermost layer or Negative electrode active material layers may be arranged on both sides.

A positive electrode current collector plate 25 and a negative electrode current collector plate 27 that are conductive to each electrode (positive electrode and negative electrode) are attached to the positive electrode current collector 11'and the negative electrode current collector 11', respectively, and the end portion of the laminate film 29 is attached. It has a structure that is led out to the outside of the laminated film 29 so as to be sandwiched between the two. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are connected to the positive electrode current collector 11'and the negative electrode current collector 11'of each electrode via the positive electrode terminal lead and the negative electrode terminal lead (not shown), respectively, as necessary. It may be attached to'by ultrasonic welding, resistance welding, or the like.

In the above description, an embodiment of the all-solid-state battery according to one embodiment of the present invention has been described by taking a laminated type (internal parallel connection type) all-solid-state lithium ion secondary battery as an example. However, the type of all-solid-state battery to which the present invention can be applied is not particularly limited, and the positive electrode active material layer electrically bonded to one surface of the current collector and the opposite surface of the current collector are electrically connected. It is also applicable to a bipolar (bipolar) all-solid-state battery including a bipolar electrode having a coupled negative electrode active material layer.

FIG. 7 is a sectional view schematically showing a bipolar type (bipolar type) all-solid-state lithium ion secondary battery (hereinafter, also simply referred to as “bipolar type secondary battery”) according to an embodiment of the present invention. .. The bipolar secondary battery 10b shown in FIG. 7 has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminated film 29 which is a battery exterior.

As shown in FIG. 7, in the power generation element 21 of the bipolar secondary battery 10b of the present embodiment, a positive electrode active material layer 13 electrically bonded to one surface of the current collector 11 is formed, and the current collector 11 has a positive electrode active material layer 13. It has a plurality of bipolar electrodes 23 having an electrically coupled negative electrode active material layer 15 formed on the opposite surface. Each bipolar electrode 23 is laminated via a solid electrolyte layer 17 to form a power generation element 21. The solid electrolyte layer 17 has a structure in which the solid electrolyte is formed into layers. At this time, the positive electrode active material layer 13 of the one bipolar electrode 23 and the negative electrode active material layer 15 of the other bipolar electrode 23 adjacent to the one bipolar electrode 23 face each other via the solid electrolyte layer 17. , The bipolar electrodes 23 and the solid electrolyte layer 17 are alternately laminated. That is, the solid electrolyte layer 17 is sandwiched between the positive electrode active material layer 13 of the one bipolar electrode 23 and the negative electrode active material layer 15 of the other bipolar electrode 23 adjacent to the one bipolar electrode 23. Has been done.

The adjacent positive electrode active material layer 13, the solid electrolyte layer 17, and the negative electrode active material layer 15 constitute one cell cell layer 19. Therefore, it can be said that the bipolar secondary battery 10b has a configuration in which the cell cell layers 19 are laminated. The positive electrode active material layer 13 is formed on only one side of the outermost layer current collector 11a on the positive electrode side located in the outermost layer of the power generation element 21. Further, the negative electrode active material layer 15 is formed on only one side of the outermost layer current collector 11b on the negative electrode side located in the outermost layer of the power generation element 21.

Further, in the bipolar secondary battery 10b shown in FIG. 7, a positive electrode current collector plate (positive electrode tab) 25 is arranged so as to be adjacent to the outermost layer current collector 11a on the positive electrode side, and this is extended to form a battery exterior. It is derived from the laminated film 29. On the other hand, the negative electrode current collector plate (negative electrode tab) 27 is arranged so as to be adjacent to the outermost layer current collector 11b on the negative electrode side, and is similarly extended and led out from the laminated film 29.

The number of times the cell cell layer 19 is laminated is adjusted according to a desired voltage. Further, in the bipolar secondary battery 10b, the number of times the cell cell layer 19 is laminated may be reduced as long as a sufficient output can be secured even if the thickness of the battery is made as thin as possible. Even in the bipolar secondary battery 10b, in order to prevent external impact and environmental deterioration during use, the power generation element 21 is vacuum-sealed in the laminated film 29 which is the battery exterior, and the positive electrode current collector plate 25 and the negative electrode current collector are collected. It is preferable to have a structure in which the electric plate 27 is taken out from the laminated film 29.

Hereinafter, the main components of the above-mentioned laminated secondary battery 10a will be described.

[Current collector]
The current collector has a function of mediating the movement of electrons from one surface in contact with the positive electrode active material layer to the other surface in contact with the negative electrode active material layer. There are no particular restrictions on the materials that make up the current collector. As a constituent material of the current collector, for example, a metal or a resin having conductivity can be adopted.

Specific examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, and the like may be used. Further, the foil may be a metal surface coated with aluminum. Of these, aluminum, stainless steel, copper, and nickel are preferable from the viewpoints of electron conductivity, battery operating potential, adhesion of the negative electrode active material by sputtering to the current collector, and the like.

Further, as the latter resin having conductivity, a resin in which a conductive filler is added to a non-conductive polymer material as needed can be mentioned.

Examples of the non-conductive polymer material include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), and polyimide. (PI), Polyethyleneimide (PAI), Polyethylene (PA), Polytetrafluoroethylene (PTFE), Styrene-butadiene rubber (SBR), Polyacrylonitrile (PAN), Polymethylacrylate (PMA), Polymethylmethacrylate (PMMA) , Polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), polystyrene (PS) and the like. Such non-conductive polymer materials can have excellent potential resistance or solvent resistance.

A conductive filler may be added to the above-mentioned conductive polymer material or non-conductive polymer material, if necessary. In particular, when the resin used as the base material of the current collector is composed of only a non-conductive polymer, a conductive filler is inevitably indispensable in order to impart conductivity to the resin.

The conductive filler can be used without particular limitation as long as it is a conductive substance. For example, materials having excellent conductivity, potential resistance, or lithium ion blocking property include metals and conductive carbon. The metal is not particularly limited, and includes at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, and Sb, or at least one of these metals. It preferably contains an alloy or metal oxide. Further, the conductive carbon is not particularly limited. Preferably, it is selected from the group consisting of acetylene black, vulcan (registered trademark), black pearl (registered trademark), carbon nanofiber, Ketjen black (registered trademark), carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. It contains at least one species.

The amount of the conductive filler added is not particularly limited as long as it can impart sufficient conductivity to the current collector, and is generally 5 to 80% by mass with respect to 100% by mass of the total mass of the current collector. Is.

The current collector may have a single-layer structure made of a single material, or may have a laminated structure in which layers made of these materials are appropriately combined. From the viewpoint of reducing the weight of the current collector, it is preferable to include a conductive resin layer made of at least a conductive resin. Further, from the viewpoint of blocking the movement of lithium ions between the cell layers, a metal layer may be provided as a part of the current collector.

[Negative active material layer]
The negative electrode active material layer contains a negative electrode active material. The negative electrode active material preferably contains metallic lithium simple substance (Li) or a lithium-containing alloy. The type of these negative electrode active materials is not particularly limited, and examples of the Li-containing alloy include alloys of Li and at least one of In, Al, Si, and Sn. In some cases, two or more kinds of negative electrode active materials may be used in combination. Of course, a negative electrode active material other than the above may be used.

Examples of the shape of the negative electrode active material include a particle shape (spherical shape, a fibrous shape), a thin film shape, and the like. When the negative electrode active material has a particle shape, its average particle size (D ₅₀ ) is preferably in the range of, for example, 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, and further preferably in the range of 100 nm. It is in the range of ~ 20 μm, and particularly preferably in the range of 1 to 20 μm. In the present specification, the value of the average particle size (D ₅₀ ) of the active material can be measured by the laser diffraction / scattering method.

The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but is preferably in the range of 40 to 99% by mass, preferably in the range of 50 to 90% by mass, for example. More preferred.

The negative electrode active material layer preferably further contains a solid electrolyte. Since the negative electrode active material layer contains a solid electrolyte, the ionic conductivity of the negative electrode active material layer can be improved. Examples of the solid electrolyte include a sulfide solid electrolyte and an oxide solid electrolyte, but since they are generally not easily affected by grain boundaries, they have a large substantial fracture toughness value (that is, cracks caused by dendrite). It is preferable to contain a sulfide solid electrolyte from the viewpoint of high ionic conductivity.

Examples of the sulfide solid electrolyte include LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ S-P ₂ O ₅ , LiI-Li ₃ PO _4- P ₂ S ₅ , Li _{2 SP 2} S ₅ , _{LiI-Li 3 PS 4, LiI} -LiBr-Li 3 PS 4, Li 3 PS 4, Li 2 S-P 2 S 5, Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 - Li ₂ O, Li ₂ S-P ₂ S _{5 -Li 2} O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS _2- LiI, Li ₂ S-SiS _2- LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS _2- B ₂ S _3- LiI, Li ₂ S-SiS _2- P ₂ S _5- LiI, Li _{2 SB 2} S ₃ , Li _{2 SP 2} S _5- Z _m S _n (where m and n are positive numbers and Z is any of Ge, Zn or Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS _{2 -Li 3} PO ₄ , Examples thereof include Li ₂ S-SiS _{2 -Li x} MO _y (where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga and In). .. The description of "Li ₂ SP ₂ S ₅ " means a sulfide solid electrolyte made by using a raw material composition containing _{Li 2} S and P ₂ S _{5, and the same applies to other descriptions.}

The sulfide solid electrolyte may have, for example, a Li ₃ PS ₄ skeleton, a Li ₄ P ₂ S ₇ skeleton, or a Li ₄ P ₂ S ₆ skeleton. .. Examples of the sulfide solid electrolyte having a Li ₃ PS _{4 skeleton include LiI-Li 3} PS ₄ , LiI-LiBr-Li ₃ PS _{4, and} Li ₃ PS ₄ . Further, examples of the sulfide solid electrolyte having a Li ₄ P ₂ S ₇ skeleton include a Li-PS-based solid electrolyte called LPS (for example, Li ₇ P ₃ S ₁₁ ). Further, as the sulfide solid electrolyte, for example, _{LGPS represented by Li (4-x)} Ge _(1-x) P _x S ₄ (x satisfies 0 <x <1) may be used. Among them, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing a P element, and the sulfide solid electrolyte is more preferably a material containing Li ₂ SP ₂ S ₅ as a main component. Further, the sulfide solid electrolyte may contain halogens (F, Cl, Br, I).

When the sulfide solid electrolyte is a Li ₂ SP ₂ S ₅ system, the ratio of Li ₂ S and P ₂ S ₅ is a molar ratio of Li ₂ S: P ₂ S ₅ = 50: 50 to 100. It is preferably in the range of: 0, and in particular, Li ₂ S: P ₂ S ₅ = 70:30 to 80:20.

Further, the sulfide solid electrolyte may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by the solid phase method. The sulfide glass can be obtained, for example, by performing mechanical milling (ball mill or the like) on the raw material composition. Further, the crystallized sulfide glass can be obtained, for example, by heat-treating the sulfide glass at a temperature equal to or higher than the crystallization temperature. The ionic conductivity (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25 ° C.) ^{is preferably 1 × 10 -5} S / cm or more ^{, for example, 1 × 10 -4} S / cm. It is more preferably cm or more. The value of the ionic conductivity of the solid electrolyte can be measured by the AC impedance method.

Examples of the oxide solid electrolyte include compounds having a NASICON type structure and the like. As an example of a compound having a NASICON type structure, a compound _{(LAGP) represented by the general formula Li 1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), a general formula Li _{1 + x} Al _x Ti ₂ Examples thereof include a compound (LATP) represented by _−x (PO ₄ ) _{3 (0 ≦ x ≦ 2).} Further, as another example of the oxide solid electrolyte, LiLaTIO (for example, Li _0.34 La _0.51 TiO ₃ ), LiPON (for example, Li _2.9 PO _3.3 N _0.46 ), LiLaZrO (for example, Li LaZrO). , Li ₇ La ₃ Zr ₂ O ₁₂ ) and the like.

Examples of the shape of the solid electrolyte include a particle shape such as a true spherical shape and an elliptical spherical shape, and a thin film shape. When the solid electrolyte has a particle shape, its average particle size (D ₅₀ ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less. On the other hand, the average particle size (D ₅₀ ) is preferably 0.01 μm or more, and more preferably 0.1 μm or more.

The content of the solid electrolyte in the negative electrode active material layer is, for example, preferably in the range of 1 to 60% by mass, and more preferably in the range of 10 to 50% by mass.

The negative electrode active material layer may further contain at least one of a conductive auxiliary agent and a binder in addition to the negative electrode active material and the solid electrolyte described above.

Examples of the conductive auxiliary agent include metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium, alloys or metal oxides containing these metals; carbon fibers (specifically, vapor-grown carbon fibers). (VGCF), polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, activated carbon fiber, etc.), carbon nanotube (CNT), carbon black (specifically, acetylene black, Ketjen black (registered trademark)) , Furness black, channel black, thermal lamp black, etc.), but is not limited to these. Further, a particulate ceramic material or a resin material coated with the above metal material by plating or the like can also be used as a conductive auxiliary agent. Among these conductive auxiliaries, from the viewpoint of electrical stability, it is preferable to contain at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon, and aluminum, stainless steel. It is more preferable to contain at least one selected from the group consisting of silver, gold, and carbon, and it is further preferable to contain at least one carbon. Only one kind of these conductive auxiliaries may be used alone, or two or more kinds thereof may be used in combination.

The shape of the conductive auxiliary agent is preferably particulate or fibrous. When the conductive auxiliary agent is in the form of particles, the shape of the particles is not particularly limited, and may be any shape such as powder, sphere, rod, needle, plate, columnar, indefinite, flint, and spindle. It doesn't matter.

The average particle size (primary particle size) when the conductive auxiliary agent is in the form of particles is not particularly limited, but is preferably 0.01 to 10 μm from the viewpoint of the electrical characteristics of the battery. In the present specification, the “particle size of the conductive auxiliary agent” means the maximum distance L among the distances between any two points on the contour line of the conductive auxiliary agent. As the value of the "average particle size of the conductive auxiliary agent", the particle size of the particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The value calculated as the average value of is adopted.

When the negative electrode active material layer contains a conductive auxiliary agent, the content of the conductive auxiliary agent in the negative electrode active material layer is not particularly limited, but is preferably 0 to 10% by mass with respect to the total mass of the negative electrode active material layer. , More preferably 2 to 8% by mass, and even more preferably 4 to 7% by mass. Within such a range, a stronger electron conduction path can be formed in the negative electrode active material layer, which can effectively contribute to the improvement of battery characteristics.

On the other hand, the binder is not particularly limited, and examples thereof include the following materials.

Polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are replaced by other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyethernitrile, polytetrafluoroethylene, Polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and its hydrogen additive , Fluoroplastic polymers such as styrene / isoprene / styrene block copolymers and their hydrogenated additives, tetrafluoroethylene / hexafluoropropylene copolymers (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymers (PFA) , Fluororesin such as ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinylfluoride (PVF), vinylidene fluoride- Hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based fluororubber), vinylidene fluoride-pentafluoropropylene-based fluororubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber) Examples thereof include vinylidene fluoride-based fluororubbers such as VDF-PFMVE-TFE-based fluororubbers, vinylidene fluoride-chlorotrifluoroethylene-based fluororubbers (VDF-CTFE-based fluororubbers), and epoxy resins. Of these, polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

The thickness of the negative electrode active material layer varies depending on the configuration of the target all-solid-state battery, but is preferably in the range of 0.1 to 1000 μm, for example.

[Positive electrode active material layer]
The positive electrode active material layer contains a positive electrode active material. The types of the positive electrode active material is not particularly limited, (any of the compounds of _Li 2 _S 8 ~Li 2 _S) elemental sulfur (S ₈₎ or reduction products of sulfur containing lithium is preferably used. Here, for example, elemental sulfur (S ₈ ) has an extremely large theoretical capacity of about 1670 mAh / g, and has the advantages of low cost and abundant resources. In this case, when the all-solid-state lithium-ion secondary battery is provided in a charged state, sulfur alone (S ₈ ) is contained as the positive electrode active material. Further, when the all-solid-state lithium-ion secondary battery is provided in a discharged state, or reduction products of sulfur containing lithium as a positive electrode active material (the compound of the above-mentioned _Li 2 _S 8 ~Li 2 _S ) Is contained.

Incidentally, the positive electrode active material layer, the positive electrode active material other than the (any of the compounds of _Li 2 _S 8 ~Li 2 _S described above) above elemental sulfur (S ₈₎ or reduction products of sulfur containing lithium It may be included. However, the ratio of sulfur alone or the reduction product of sulfur containing lithium to the positive electrode active material contained in the positive electrode active material layer is preferably 50 to 100% by mass, and more preferably 80 to 100% by mass. , More preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, particularly preferably 98 to 100% by mass, and most preferably 100% by mass.

Examples of the positive electrode active material other than elemental sulfur or the reduction product of sulfur containing lithium include disulfide compounds, sulfur-modified polyacrylonitrile represented by the compounds described in WO 2010/0444437, and sulfur-modified polyisoprene. , Rubianic acid (dithiooxamide), polycarbon sulfide and the like. Inorganic sulfur compounds such as S-carbon composite, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , MoS ₂ , and MoS _{3 can also be used.} Further, examples of the sulfur-free positive electrode active material include layered rock salt type active materials _{such as LiCoO 2} , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and Li (Ni-Mn-Co) O _{2 , LiMn 2} O ₄ , LiNi. Examples thereof include spinel-type active materials such as _0.5 Mn _1.5 O ₄ , olivine-type active materials such as _{LiFePO 4} and LiMnPO ₄ , and Si-containing active materials such as _{Li 2} FeSiO ₄ and Li _{2 MnSiO 4.} Examples of the oxide active material other than the above include Li ₄ Ti ₅ O ₁₂ . In some cases, two or more kinds of positive electrode active materials may be used in combination. Needless to say, a positive electrode active material other than the above may be used.

Examples of the shape of the positive electrode active material include a particle shape (spherical shape, a fibrous shape), a thin film shape, and the like. When the positive electrode active material has a particle shape, its average particle size (D ₅₀ ) is preferably in the range of, for example, 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, and further preferably in the range of 100 nm. It is in the range of ~ 20 μm, and particularly preferably in the range of 1 to 20 μm. In the present specification, the value of the average particle size (D ₅₀ ) of the active material can be measured by the laser diffraction / scattering method.

The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is preferably in the range of 40 to 99% by mass, and preferably in the range of 50 to 90% by mass. More preferred. The positive electrode active material layer may further contain at least one of a solid electrolyte, a conductive auxiliary agent, and a binder, as required, as in the case of the negative electrode active material layer described above. Since the specific forms of these materials are the same as those described above, detailed description thereof will be omitted here.

[Solid electrolyte layer]
The solid electrolyte layer of the bipolar secondary battery according to the present embodiment contains a solid electrolyte as a main component and is a layer interposed between the positive electrode active material layer and the negative electrode active material layer described above. Since the specific form of the solid electrolyte contained in the solid electrolyte layer is the same as that described above, detailed description thereof will be omitted here.

The content of the solid electrolyte in the solid electrolyte layer is, for example, preferably in the range of 10 to 100% by mass, more preferably in the range of 50 to 100% by mass, and in the range of 90 to 100% by mass. Is more preferable.

The solid electrolyte layer may further contain a binder in addition to the solid electrolyte described above. Since the specific form of the binder that can be contained in the solid electrolyte layer is the same as that described above, detailed description thereof will be omitted here.

The thickness of the solid electrolyte layer varies depending on the configuration of the target bipolar secondary battery, but is preferably in the range of 0.1 to 1000 μm, preferably in the range of 0.1 to 300 μm. Is more preferable.

[Positive current collector plate and negative electrode current collector plate]
The material constituting the current collector plates (25, 27) is not particularly limited, and a known highly conductive material conventionally used as a current collector plate for a secondary battery can be used. As the constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. The same material may be used or different materials may be used for the positive electrode current collector plate 25 and the negative electrode current collector plate 27.

[Positive lead and negative electrode lead]
Further, although not shown, the current collector 11 and the current collector plates (25, 27) may be electrically connected via a positive electrode lead or a negative electrode lead. As the constituent materials of the positive electrode and the negative electrode leads, materials used in known lithium ion secondary batteries can be similarly adopted. The part taken out from the exterior is heat-shrinkable with heat-resistant insulation so that it does not come into contact with peripheral devices or wiring and cause electric leakage, which affects products (for example, automobile parts, especially electronic devices). It is preferable to cover with a tube or the like.

[Battery exterior]
As the battery exterior, a known metal can case can be used, and as shown in FIGS. 6 and 7, a bag-shaped case using a laminated film 29 containing aluminum, which can cover the power generation element, is used. Can be done. As the laminate film, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used, but the laminate film is not limited thereto. A laminated film is desirable from the viewpoint of high output and excellent cooling performance, and can be suitably used for batteries for large devices for EVs and HEVs. Further, since the group pressure applied to the power generation element from the outside can be easily adjusted, a laminated film containing aluminum is more preferable for the exterior body.

FIG. 8 is a perspective view showing the appearance of a flat lithium ion secondary battery, which is a typical embodiment of a laminated secondary battery.

As shown in FIG. 8, the flat laminated secondary battery 50 has a rectangular flat shape, and positive electrode tabs 58 and negative electrode tabs 59 for extracting electric power are pulled out from both side portions thereof. There is. The power generation element 57 is wrapped by the battery exterior (laminate film 52) of the laminated secondary battery 50, and the periphery thereof is heat-sealed. The power generation element 57 pulls out the positive electrode tab 58 and the negative electrode tab 59 to the outside. It is sealed in a closed state. Here, the power generation element 57 corresponds to the power generation element 21 of the laminated secondary battery 10a shown in FIG. 6 described above.

The lithium ion secondary battery is not limited to a laminated flat battery. The wound lithium-ion secondary battery may have a cylindrical shape, or may be formed by deforming such a cylindrical shape into a rectangular flat shape. There are no particular restrictions. The cylindrical shape is not particularly limited, for example, a laminated film may be used for the exterior body, or a conventional cylindrical can (metal can) may be used. Preferably, the power generation element is exteriorized with an aluminum laminate film. By this form, weight reduction can be achieved.

Further, the extraction of the tabs 58 and 59 shown in FIG. 8 is not particularly limited. The positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of each and taken out from each side. It is not limited to. Further, in the winding type lithium ion battery, the terminal may be formed by using, for example, a cylindrical can (metal can) instead of the tab.

[Battery set]
An assembled battery is formed by connecting a plurality of batteries. More specifically, it is composed of serialization, parallelization, or both by using at least two or more. By connecting in series or in parallel, the capacitance and voltage can be adjusted freely.

It is also possible to connect a plurality of batteries in series or in parallel to form a small assembled battery that can be attached / detached. Then, by connecting a plurality of these detachable small assembled batteries in series or in parallel, a large capacity and a large capacity suitable for a vehicle driving power source or an auxiliary power source that require a high volume energy density and a high volume output density. It is also possible to form an assembled battery having an output. How many batteries are connected to make an assembled battery, and how many stages of small assembled batteries are stacked to make a large-capacity assembled battery depends on the battery capacity of the vehicle (electric vehicle) to be installed. It may be decided according to the output.

When carrying out the charging method according to the present invention for an assembled battery, for example, the charging process can be executed while measuring the internal resistance value of each of the individual batteries (single cells) constituting the assembled battery. With such a configuration, it is possible to perform the charging process while separately executing the control for reducing the internal resistance of each of the individual batteries (single cell).

[vehicle]
The non-aqueous electrolyte secondary battery of this embodiment maintains the discharge capacity even after long-term use and has good cycle characteristics. In addition, the volumetric energy density is high. In vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles, higher capacity and larger size are required and longer life is required compared to electric and portable electronic device applications. .. Therefore, the non-aqueous electrolyte secondary battery can be suitably used as a power source for a vehicle, for example, a vehicle drive power source or an auxiliary power source.

Specifically, a battery or an assembled battery formed by combining a plurality of batteries can be mounted on the vehicle. In the present invention, a long-life battery having excellent long-term reliability and output characteristics can be configured. Therefore, when such a battery is installed, a plug-in hybrid electric vehicle having a long EV mileage or an electric vehicle having a long one-charge mileage can be configured. .. In addition to hybrid vehicles, fuel cell vehicles, electric vehicles (all four-wheeled vehicles (commercial vehicles such as passenger cars, trucks, buses, light vehicles, etc.)) This is because it becomes a highly reliable automobile with a long life by using it for two-wheeled vehicles (including motorcycles) and three-wheeled vehicles. However, the application is not limited to automobiles, and can be applied to various power sources of other vehicles, for example, moving objects such as trains, and power supplies for mounting such as uninterruptible power supplies. It is also possible to use it as.

[Experimental example]
For the purpose of confirming the feasibility of the present invention, by performing the charging process using a current (heating current) larger than the rated charging current, the charging process is performed with the rated charging current as compared with the case where the charging process is performed. Therefore, a simulation experiment was conducted to confirm that the time required for the battery temperature rise was shortened.

First, for a commercially available all-solid-state lithium-ion secondary battery (positive electrode active material: sulfur (S), negative electrode active material: metallic lithium (Li)), the initial internal resistance value was measured, and the rate of increase in internal resistance was measured. The internal resistance value was calculated assuming that Then, assuming that the internal resistance value corresponds to the electrolyte resistance, the amount of heat corresponding to Joule heat calculated from the current value to be energized was calculated.

On the other hand, the amount of heat required to raise the temperature of the battery from room temperature (20 ° C.) to the upper limit temperature is determined from the heat capacity of the battery obtained from the constituent materials of the secondary battery and the value of the upper limit temperature set in advance. Calculated. Then, assuming that all the heat equivalent to the Joule heat described above is used to raise the temperature of the battery, the energization time required to raise the temperature of the battery from room temperature (20 ° C.) to the upper limit temperature is energized. It was calculated and compared for each current value. The upper limit temperature was set to 115 ° C. in view of the fact that the melting point of metallic lithium (Li), which is the material having the lowest melting point among the power generation elements of the battery, is 115.2 ° C.

The results of the above simulation experiment performed using a current value equivalent to normal charging (3 kW single-phase 200 V) are shown in Table 1 below. In this experiment, the value of the charging current was set to 15A, 18A or 22.5A.

Similarly, the results of the above simulation experiment performed using a current value equivalent to quick charging (50 kW) are shown in Table 2 below. In this experiment, the value of the charging current was set to 125A, 150A or 187.5A.

As can be seen from the results shown in Tables 1 and 2, it can be seen that as the value of the charging current is increased, the time required to raise the temperature of the battery is shortened. Therefore, in the control in the secondary battery system or the charging device for the secondary battery according to the present invention, when the increase in the internal resistance value of the battery is detected, the temperature of the battery is raised by using the heating current, and the solid electrolyte is used. It is expected that the internal resistance value can be reduced (recovered) in an extremely short time by melting the material at the layer-electrode active material layer interface.

1 All-solid-state lithium-ion secondary battery system,
2 All-solid-state lithium-ion secondary battery,
3 Voltage sensor,
4 temperature sensor,
5 Voltage / current adjuster,
6 current sensor,
7 Control unit,
8 external power supply,
10a, 50 stacked secondary batteries,
10b bipolar secondary battery,
11 Current collector,
11'Positive current collector,
11'' Negative electrode current collector,
11a Outermost layer current collector on the positive electrode side,
11b Outermost layer current collector on the negative electrode side,
13 Positive electrode active material layer,
15 Negative electrode active material layer,
17 Electrolyte layer,
19 Single battery layer,
21,57 Power generation elements,
23 Bipolar electrode,
25 Positive electrode current collector plate (positive electrode tab),
27 Negative electrode current collector plate (negative electrode tab),
29, 52 Laminated film,
58 Positive tab,
59 Negative tab,
71 CPU,
72 Memory
100 battery pack,
110 rechargeable battery module,
120 Battery Management System (BMS),
130 junction box,
200 DC / DC junction box,
210 DC / DC converter,
220 Normal charging relay,
221 In-vehicle charger,
222 Normal charging port,
230 quick charge relay,
232 Fast Charge Port 240 Starter Motor (SM),
250 electrical load,
260 Alternator (ALT),
300 power circuit,
310 Main battery (lead-acid battery),
320 sub-battery (all-solid-state battery),
330 relay.

Claims (7)

A positive electrode containing a positive electrode active material layer containing a positive electrode active material, and a positive electrode
A negative electrode containing a negative electrode active material layer containing a negative electrode active material, and a negative electrode
A solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer,
With an all-solid-state lithium-ion secondary battery equipped with a power generation element,
A charger for charging the all-solid-state lithium-ion secondary battery and
An internal resistance measuring unit that measures the internal resistance of the all-solid-state lithium-ion secondary battery,
When the charger charges the all-solid-state lithium-ion secondary battery, when the internal resistance value measured by the internal resistance measuring unit or the rate of increase with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. A control unit that controls the charger so as to charge the all-solid-state lithium-ion battery with a heating current larger than the rated charging current.
All-solid-state lithium-ion secondary battery system. After the all-solid-state lithium-ion battery is charged by the heating current,
The control unit is used for heating when the internal resistance value or the rate of increase is less than the threshold value, or when the battery temperature of the all-solid-state lithium-ion battery is equal to or higher than a predetermined threshold temperature. The all-solid-state lithium-ion secondary battery system according to claim 1, wherein charging with an electric current is stopped and the charger is controlled so as to charge the all-solid-state lithium-ion battery with the rated charging current. The control unit controls the magnitude and / or application time of the heating current so that the maximum temperatures of the positive electrode active material and the negative electrode active material after the application of the heating current are lower than the respective melting points. The all-solid-state lithium-ion secondary battery system according to claim 1 or 2. The all-solid-state lithium-ion secondary battery is mounted on the vehicle, and the charger uses the power supplied from a power source installed outside the vehicle to supply the all-solid-state lithium-ion secondary battery with the heating current. The all-solid-state lithium ion secondary battery system according to any one of claims 1 to 3. The all-solid-state lithium-ion secondary battery is mounted on the vehicle, and the charger uses the power supplied from another power source mounted on the vehicle to supply the all-solid-state lithium-ion secondary battery with the heating current. The all-solid-state lithium ion secondary battery system according to any one of claims 1 to 3. The all-solid-state lithium ion II according to any one of claims 1 to 5, wherein the positive electrode active material contains a simple sulfur or a reduction product of sulfur containing lithium, and the negative electrode active material contains a simple metallic lithium. Next battery system. A charging device for charging all-solid-state lithium-ion secondary batteries.
A charger for charging the all-solid-state lithium-ion secondary battery and
An internal resistance measuring unit that measures the internal resistance of the all-solid-state lithium-ion secondary battery,
When the charger charges the all-solid-state lithium-ion secondary battery, when the internal resistance value measured by the internal resistance measuring unit or the rate of increase with respect to the initial internal resistance value is equal to or higher than a predetermined threshold value. A control unit that controls the charger so as to charge the all-solid-state lithium-ion battery with a heating current larger than the rated charging current.
A charging device for all-solid-state lithium-ion secondary batteries.

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